simple theory question for all SC proponents.  so simple in fact what am i missing?

we have 13M BTC @ around $325.  SC comes along and lets say 3M BTC --> scBTC (just for illustration).  we know that the price of scBTC has to be lower given MM, newness, being unproven, risk of failure, etc.  let's say price starts off @ $100. $325

why don't arb bots circle back around and drive BTC price down to say $250-270?  multiply this by 1000 SC's.